Numerical modelling of methane oxidation efficiency and coupled water-gas-heat reactive transfer in a sloping landfill cover

S. Feng, C. W. W. Ng, A. K. Leung, H. W. Liu (Lead / Corresponding author)

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)
151 Downloads (Pure)

Abstract

Microbial aerobic methane oxidation in unsaturated landfill cover involves coupled water, gas and heat reactive transfer. The coupled process is complex and its influence on methane oxidation efficiency is not clear, especially in steep covers where spatial variations of water, gas and heat are significant. In this study, two-dimensional finite element numerical simulations were carried out to evaluate the performance of unsaturated sloping cover. The numerical model was calibrated using a set of flume model test data, and was then subsequently used for parametric study. A new method that considers transient changes of methane concentration during the estimation of the methane oxidation efficiency was proposed and compared against existing methods. It was found that a steeper cover had a lower oxidation efficiency due to enhanced downslope water flow, during which desaturation of soil promoted gas transport and hence landfill gas emission. This effect was magnified as the cover angle and landfill gas generation rate at the bottom of the cover increased. Assuming the steady-state methane concentration in a cover would result in a non-conservative overestimation of oxidation efficiency, especially when a steep cover was subjected to rainfall infiltration. By considering the transient methane concentration, the newly-modified method can give a more accurate oxidation efficiency.

Original languageEnglish
Pages (from-to)355-368
Number of pages14
JournalWaste Management
Volume68
Early online date22 May 2017
DOIs
Publication statusPublished - Oct 2017

Keywords

  • Journal article
  • Methane oxidation
  • Reactive transport
  • Coupled water-gas-heat
  • Sloping landfill cover

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